Aspartic esters represent a unique class of reactants in adhesive, coating, and sealant formulations. Their reactivity typically lies between slow classical polyols and faster reacting primary and secondary amines.
U.S. Pat. Nos. 5,412,056, 5,623,045, 5,126,170, and 5,821,326 disclose coating compositions in which the binding agent is a two-component system containing a polyisocyanate component and an isocyanate-reactive component. The latter component includes at least one aspartic acid diester group formed by reacting an amine with a maleic or fumaric diester.
EP 0 667 362 A1 discloses coating compositions including a polyisocyanate component, a component that includes at least one aspartic acid diester group formed by reacting an amine with a maleic or fumaric diester, and a water-adsorbing zeolite.
Adhesives are commonly used to join or fasten two or more adherends. Adherends are considered as being any two or more materials, or pieces of material that are being joined together, including wood, metals, plastics, paper, ceramics, stone, glass, concrete, etc. Adhesives used for these purposes are based on a wide range of technologies, including elastomer/solvent/resin mixtures, epoxies, latexes, polyurethanes, silicones, cyanoacrylates, acrylics, hot melts, and others. Such adhesives can have one or more drawback, such as they may contain solvents which are toxic and often flammable, they can be incompatible with one or more classes of adherends, they can have undesirably long cure times and in many cases the bonds they form of are of insufficient strength.
It is often desirable for coatings applied to substrates to provide a desirable appearance, in many cases by applying multiple coating layers, the last of which can be a pigmented or unpigmented topcoat. Unfortunately, as the article containing the coated substrate ages, scratches that occur through normal “wear and tear”, tend to deteriorate the appearance of the coated surface of the substrate,
A sealant is typically a thin film, often containing a plastic, that is applied onto one or more surfaces on one or more substrates to prevent passage of a liquid or gas through the film. The sealant can be used to prevent exposure of the substrate or is often additionally used to prevent exposure via defects in a substrate or between gaps that can exist between substrates.
Oftentimes, high molecular weight compounds containing aspartic esters are desired for various adhesive, coating and sealant applications. However, the corresponding precursors often react very slowly leading to undesirably long processing times, poor conversion to the desired product, and/or impure products.
Additionally, desired functionality and/or molecular architectures in the aspartic ester materials may not be achievable using the established amine-maleic/fumaric ester synthetic pathway. This limits the possible aspartic ester containing materials available for formulation.
U.S. Pat. No. 2,569,200 discloses polyvalent alkylene imine esters and methods for preparing them.
There is an established need in the art for alternative synthetic pathways that can provide a wider range of molecular architectures and functional groups for aspartic ester containing compounds that can be made efficiently.